I've heard this talk of Kronans, but I'm not sure where it came from. Did someone working in the movie said they'd be there, or was there footage at comic con, or what?

I'm pumped that they're in. I hope alien gods (kinda like in TheGod Butcher) are mentioned or briefly seen. And of course Olympians (they might be able to wait til Thor 3). And then the standard Badoon, Korbinites, and all mythological species. Not all of them in The Dark World, but in the third movie and hopefully fourth as well.